Legally the president doesn’t have the power to unilaterally go to war, but that hasn’t stopped them from doing it for the last 70+ years.
Basically ever modern president has grabbed more power for the executive branch without being properly checked by congress or the courts. Combine that with an ever expanding military and surveillance apparatus and it turns out you can do some pretty bad stuff, regardless of the legality.
As for the rest of it, idk man. Clearly you have your rosy view of history where the US was a super great place before the scary Russians came in to corrupt democracy. All I can say is you have more reading to do.
Maybe we don’t want to do that again… people have some really short memories.